This invention is related to lubricating oils, lubricating oil additives, and more particularly to a dispersant composition in the oil or additive, the dispersant formed from the Mannich reaction of a polyphenolic compound with a succinimide. The compositions of the present invention may further be posted-treated to form derivatized dispersants.
Internal combustion engines operate under a wide range of temperatures including low temperature stop-and-go service as well as high temperature conditions produced by continuous high speed driving. Stop-and-go driving, particularly during cold, damp weather conditions, leads to the formation of sludge in the crankcase and in the oil passages of a gasoline or a diesel engine. This sludge seriously limits the ability of the crankcase oil to effectively lubricate the engine. In addition, the sludge with its entrapped water tends to contribute to rust formation in the engine. These problems tend to be aggravated by the manufacturer""s lubrication service recommendations, which specify extended oil drain intervals.
It is known to employ nitrogen containing dispersants and/or detergents in the formulation of crankcase lubricating oil compositions. Many of the known dispersant/detergent compounds are based on the reaction of an alkenylsuccinic acid or anhydride with an amine or polyamine to produce an alkylsuccinimide or an alkenylsuccinic acid as determined by selected conditions of reaction.
Also it is known to chlorinate alkenylsuccinic acid or anhydride prior to the reaction with an amine or polyamine in order to produce a reaction product in which a portion of the amine or polyamine is attached directly to the alkenyl radical of the alkenyl succinic acid or anhydride. The thrust of many of these processes is to produce a product having a relatively high level of nitrogen in order to provide improved dispersancy in a crankcase lubricating oil composition.
With the introduction of four cylinder internal combustion engines which must operate at relatively higher engine speeds or RPM""s than conventional 6-and 8-cylinder engines in order to produce the required torque, it has become increasingly difficult to provide a satisfactory dispersant anti-oxidant lubricating oil composition.
Recessive valve train wear, piston deposits, and oil thickening can occur at high engine operating temperatures with poorly formulated lubricating oils. Valve train wear and piston deposits can cause engine malfunction and in some cases result in engine failure. Excessive oxidative oil thickening can prevent the oil from flowing to the engine""s oil pump causing the engine to seize due to lack of lubrication.
The conventional sludge dispersants for lubricating oils have been of the polyisobutenyl succinimide type for over 20 years. Recent changes in test procedures have made it more difficult to qualify these types of dispersants for use in lubricating oils without substantially increasing their treating dosage.
Embodiments of the present invention are directed to a dispersant composition and a method of preparing a dispersant composition. This dispersant is included in a lubricating oil or as an additive for a lubricating oil. The lubricant dispersant has a high molecular weight. It is prepared by cross-linking a conventional succinimide (for example a bis-alkenyl succinimide) under Mannich reaction conditions with a polyphenolic compound. The resulting cross-linked dispersant, having more than one aromatic moiety, is a dispersant composition with an increased ability to suspend sludge and soot. The amount of cross-linking, and the resulting size of the reaction product dispersant can be varied by changing the molecular equivalent ratios of succinimide and polyphenol in the reaction steps.
The succinimide is the reaction product of a long chain hydrocarbyl-substituted succinic acylating agent and a polymine. The long chain hydrocarbon group is for example (C2-C10) polymer, e.g., a (C2-C5) monoolefin, the polymer having a number average molecular weight (Mn) of about 500 to about 10,000. Exemplary olefin polymers for reaction with the unsaturated dicarboxylic acid anhydride or ester are polymers comprising a major molar amount of (C2-C10) polymer, e.g., a (C2-C5) monoolefin. Such olefins include ethylene, propylene, butylene, isobutylene, pentene, 1-octene, styrene, etc. The polymers can be homopolymers such as polyiosbutylene, as well as copolymers of two or more of such olefins such as copolymers of: ethylene and propylene, butylene and isobutylene, propylene and isobutylene, etc. Other copolymers include those in which a minor molar amount of the copolymers e.g., 1 to 10 mole % is a (C4-C10) non-conjugated diolefin, e.g., a copolymer of isobutylene and butadiene; or a copolymer of ethylene, propylene and 1,4-hexadiene; etc. The bis-alkenyl succinimide, in one example, has a succinic anhydride to polyisobutylene ratio ranging from 0.9 to 4.0, and has an anhydride to amine ratio ranging from 1:1 to 3:1.
In some cases, the olefin polymer may be completely saturated, for example an ethylene-propylene copolymer made by a Ziegler-Natta synthesis using hydrogen as a moderator to control molecular weight. In one example, the alpha- and beta-unsaturated dicarboxylic acid anhydride is reacted with the saturated ethylene-propylene copolymer utilizing a radical initiator.
The long chain hydrocarbyl-substituted succinic acylating agent, e.g. acid or anhydride, includes a long chain hydrocarbon, generally a polyolefin, substituted typically with an average of at least about 0.8 per mole of polyolefin, of an alpha- or beta-unsaturated (C4-C10) dicarboxylic acid, anhydride or ester thereof, such as fumaric acid, itaconic acid, maleic acid, maleic anhydride, chloromaleic acid, dimethylfumarte, chloromaleic anhydride, acrylic acid methacrylic acid, crotonic acid, cinnamic acid, and mixtures thereof.
An alkenyl succinic acid anhydride may be characterized by the following formula: 
In the above formula, R1 may be residue (containing residual unsaturation) from a polyolefin, which was reacted with maleic acid anhydride to form the alkenyl succinic acid anhydride. R1 may have a number average molecular weight (Mn) ranging from about 500-10,000, for example about 1000-5000, and for another example from about 2000-2500.
The polyamine compositions which may be employed may include primary and/or secondary amines. The amines may typically be characterized by the formula: 
In this formula, xe2x80x9caxe2x80x9d may be an integer of about 3 to about 8, for example about 5; and may be 0 or 1. In the above compound, R2 may be hydrogen or a hydrocarbon group selected from the group consisting of alkyl, aralkyl, cycloalkyl, aryl, alkaryl, alkenyl, and alkynyl, including such radicals when inertly substituted. Exemplary R3 groups may be hydrogen or lower alkyl group, i.e. C1-C10 alkyl, groups including, e.g., methyl, ethyl, n-propyl, i-propyl, butyls, amyls, hexyls, octyls, decyls, etc. R3 may be hydrogen. R2 may be a hydrocarbon selected from the same group as R3 subject to the fact that R2 is divalent and contains one less hydrogen. In one example, R3 is hydrogen and R2 is xe2x80x94CH2CH2xe2x80x94. The preferred amines are polyamines and hydroxyamines. Examples, of polyanines that may be used include, but are not limited to, aminoguanidine bicarbonate (AGBC), diethylene triamine (DETA), triethlene tetramine (TETA), tetraethylene pentamine (TEPA), pentaethylene hexamine (PEHA) and heavy polyamines. A heavy polyamine is a mixture of polyalkylenepolyamines comprising small amounts of lower polyamine oligomers such as TEPA and PEHA but primarily oligomers with 7 or more nitrogens, 2 or more primary amines per molecule, and more extensive branching than conventional polyamine mixtures. Other examples of succinimide reaction polyamines and other reagents are set forth in U.S. Pat. No. 6,548,458 B2, incorporated by reference herein in its entirety.
Representative aldehydes for use in the Mannich reaction of the present invention include the aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, caproaldehyde, heptaldehyde, stearaldehyde. Aromatic aldehydes that may be used include benzaldehyde and salicylaldehyde. Illustrative heterocyclic aldehydes for use herein are furfural and thiophene aldehyde, etc. Also useful as aldehydes in the present invention are formaldehyde-producing reagents such as paraformaldehyde, or aqueous formaldehyde solutions such as formalin. In an example, the aldehyde is formaldehyde or formalin.
A xe2x80x9cpolyphenolic compoundxe2x80x9d is one having a plurality of aromatic moeties therein. An example of a polyphenolic compound is Bis Phenol A, a condensation product of acetone and phenol. Other polyphenolic compounds include but are not limited to 2,2xe2x80x2 biphenol, 4,4xe2x80x2 biphenol, 1,6 dihyroxynaphthalene, 2,6 dihyroxynaphthalene, 2,7 dihyroxynaphthalene and a low molecular weight resole (C12 alkyl phenol formaldehyde resin) as taught in U.S. Pat. No. 6,176,886, incorporated herein by reference.
The ratio of polyphenolic compound, for instance, Bis Phenol A, to succinimide range is from 10:1 to 1:5. The ratio may be is from 1:1 to 1:3. The ratio of polyphenolic compound, for example Bis Phenol A, to formaldehyde ranges from 1:5 to 1:1. The ratio may be from 1:3 to 1:2. By varying these ratios, the amount of cross-linked reaction product can be controlled.
One method of actually performing a reaction includes the following steps. The formation of a succinimide has already been discussed earlier herein. The succinimide, for purpose of this example a bis-alkenyl succinimide, and process oil are combined and heated to between 70 and 170xc2x0 C. under nitrogen. Bis Phenol A (a polyphenol) is added and stirred. The formaldehyde solution (containing a molecular equivalent excess of aldehyde) is added and the reaction mixture is heated at between 100-170xc2x0 C. for between 2-6h. The reaction product is then cooled and filtered.
The lubricating oil, or an additive to a lubricating oil, will contain the novel reaction product described above in a concentration ranging from about 0.1 to 30 weight percent. A concentration range for an additive ranging from about 0.5 to 15 weight percent based on the total weight of the oil composition is one example with another example concentration range being from about 1 to 8.0 weight percent.
Oil concentrates of the additives may contain from about 1 to 75 weight percent of the additive reaction product in a carrier or diluent oil of lubricating oil viscosity.
The reaction product may be employed in lubricant compositions together with conventional lubricant additives. Such additives may include additional dispersants, detergents, antioxidants, pour point depressants, anti-wear agents and the like.